[TTalma]

I am using hall effect homing switches. They are all 12V, with a 12v output signal. My input board is a smooth stepper, that only wants to see 5v, I have a circuit I can wire up to use this directly, but I was thinking of using relays.

I was thinking about using 12V relays, and wiring it so that the output would be 5V ttl.

If I use relays is the switching time of a relay consistent enough that my homing will be consistent?

I'm only looking for around .005" of accuracy from the machine. But all inaccuracy adds up, so my goal is to do the best I can at each stage.

[CitizenOfDreams]

I would prefer an electronic level shifter to a mechanical relay in this situation. As you said, "all inaccuracy adds up".

[wizard]

Mechanical contacts are not reliable at 5VDC. You will need a relay with dry contacts or gold contacts. Even then you still have a mechanical system and bounce to deal with.

The better avenue here is to make use of isolator chips to accomplish both isolation and level shifting. I say isolator chips because in the past optical isolators where the common choice but these days you have other options.

By the way im not familiar with smooth stepper, isolators might be redundant here. Level shifter chips are also a possibility. If the inputs are completely isolated already you have other options to consider such as simply current limiting. In the end relays would be about the worse choice for a stepper base system the relies upon switch accuracy.